This project proposes to prepare and characterize antigens from tubercle bacilli, fungi and from some non-acid-fast bacteria. These will be employed with procedures that detect and measure the primary interactions between them and antibodies to develop tests for diagnostic and prognostic purposes. These tests are also to provide information to improve our understanding of the significance of circulating antibodies in these diseases and to evaluate their relative role in the pathogenesis of tuberculosis and other bacterial infections. It will be of special interest to determine what immunogen(s) may be responsible for antibodies to components of microorganisms found in sera from well persons and animals with no history of exposure to these organisms. Experiments will be carried out to determine if such immunogen(s) play a role in the development of immunity by either humoral or cellular mechanisms or both. The relative contributions of bone marrow and thymus cells to the development of resistance to experimental bacterial infections will be investigated. An additional objective will be to investigate the possible role of antibodies in the frequently observed anti-tumor effects of BCG. All these studies will be based on previous findings from this laboratory that have shown that antibodies to bacteria are frequently found in sera from normal persons and that there is widespread shared and/or crossreactivity among antigens from mycobacteria and taxonomically unrelated microorganisms.